The invention relates to an impact beam for a motor vehicle and method for production of an impact beam.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
The document U.S. Pat. No. 8,201,861 B2 discloses for example an impact beam as bumper made of an aluminum section, wherein a front wall, a rear wall and three transverse walls, which connect the front wall and the rear wall, enclose two hollow chambers. The impact beam is made of an extruded section.
The document DE 10 2010 050 013 A1 discloses an impact beam as bumper for a motor vehicle made of an extruded main part with a top-hat shaped cross section, and a front part which closes the main part. Both parts are interconnected by welding so as to overlap with each other. A disadvantage is the plurality of required parts that correspondingly require positioning means during production and also tolerance problems.
The documents DE 11 2007 002 534 T5, DE 603 01 916 T2, DE 100 44 409 A1 and U.S. Pat. No. 2,015,097 384 A11 disclose impact beams as bumpers for a motor vehicle, which are formed by roll-forming from a sheet metal band into a closed section, thereby forming two or more hollow chambers. A special configuration of the front wall and/or the rear wall, either in the form of ribs extending in longitudinal direction, in form of an additional hollow chamber in the front wall or in the form of concavities on the rear side can increase bending stiffness and energy absorption in the event of an impact. The document EP 0 876 265 B1 describes an impact beam as bumper for a motor vehicle, wherein a front wall, a rear wall and two transverse walls which connect the front wall and the rear wall are produced in one piece and from the same material from lightweight metal directly by extrusion so as to enclose a hollow chamber. The rear wall has hereby a greater wall thickness, wherein a cross sectional course varies along the length of the impact beam and is adapted to the load requirements.
A disadvantage is that in the case of extrusion into the section having the extruded hollow chamber production speeds have to be un-proportionally lowered with increasing strength of the aluminum alloy. The cooling of the tool is so costly that increasing demands on the lightweight construction are no longer economically feasible.
It would therefore be desirable and advantageous to provide impact beams made of lightweight metal with improved lightweight properties and low production complexity.